Show premium stickers lock icon.

Telegram/SourceFiles/chat_helpers/stickers_list_widget.h

@@ -330,6 +330,7 @@ private:
 	void addSearchRow(not_null<Data::StickersSet*> set);
 
 	void showPreview();
+	void validatePremiumLock();
 
 	Ui::MessageSendingAnimationFrom messageSentAnimationInfo(
 		int section,
@@ -390,6 +391,8 @@ private:
 	base::Timer _previewTimer;
 	bool _previewShown = false;
 
+	QImage _premiumLock;
+
 	std::map<QString, std::vector<uint64>> _searchCache;
 	std::vector<std::pair<uint64, QStringList>> _searchIndex;
 	base::Timer _searchRequestTimer;